Research On Real-time Dynamic Temperature Modeling And Experiment Of Wet Clutch

The wet clutch has the advantages of large transmission torque,smooth shifting and high stability,which can not only ensure the power of the vehicle but also greatly improve the driving comfort of the vehicle.Therefore,the wet clutch is more widely used in automatic transmissions.During the engagement process of the wet clutch,the friction pair generates a large amount of heat energy due to the relative sliding friction to increase the temperature of the clutch,causing the clutch to fail and affecting the performance of the transmission.This subject conduct research on the temperature characteristics of the friction pair of wet clutches,and establishes a real-time dynamic temperature model suitable for the whole vehicle.This model has the advantages of less memory occupation of the controller and short calculation time.(1)The relevant theories involved in the engagement process of the wet clutch are studied.Based on the friction transmission mechanism,the mathematical models of oil film pressure,asperity contact,bearing capacity and torque are established,the differential equation of thermal conductivity is deduced,and the constant solution conditions of the temperature field and the interaction of the heat-fluid-structure interaction of the friction pair are analyzed and solved.(2)The solid finite element model and the fluid finite element model of the friction pair are established respectively.The solid model and the fluid model are coupled with each other by the strong coupling method,and the heat-fluid-structure coupling model of the friction pair is established.The temperature field distribution of the steel plate and the friction lining is obtained by simulation,the maximum temperature and radial temperature gradient of the two middle steel plates are higher than those of the other two steel plates,and the temperature of the friction lining is lower than the temperature of the steel plate.So it is determined to select the two steel plates in the middle of the friction pair,which provides a theoretical basis for the establishment of the real-time dynamic temperature model.(3)The dynamic model of the automobile transmission system is established,and the changes of the speed and the sliding friction power of the wet clutch when the automobile starts off on different slopes are simulated and analyzed.According to the cooling conditions of the pair,the concepts of temperature rise power coefficient and cooling power coefficient are introduced,and a real-time dynamic temperature model is established.At the same time,the simulation results of the dynamic model are used as the input conditions of the temperature model,and the steel plate and the temperature under different working conditions are obtained.The oil outlet temperature prediction results,and the influence of cooling oil temperature and flow rate are analyzed.(4)Based on the comprehensive performance test bench of the wet clutch,the test plan for the temperature measurement during the sliding friction process of the wet clutch friction pair was formulated in detail,including the arrangement of temperature sensors,data transmission and data acquisition methods.The temperature results under the conditions of differential speed,medium slip speed and high slip speed are compared and analyzed by the real-time dynamic temperature model simulation results and the test data.The results show that in the heating stage,the temperature prediction is basically consistent with the test results,and can be accurately predicted the maximum temperature of the steel plate is obtained,which verifies the validity of the temperature model.